1. Field of the Invention
The present invention relates to steering wheels for vehicles, and more particularly to steering wheels that are formed integrally with pads and ring surface layers.
2. Description of the Related Art
A typical steering wheel includes an annular gripping ring and a pad. The pad is located at the center of the ring and connected to the ring by a plurality of spokes. A metal ring core is embedded in the ring while a metal spoke core is embedded in the spokes. A boss plate is connected to the spoke core below the pad to connect the steering wheel to a steering shaft. In this type of steering wheel, fasteners such as bolts are employed to fasten the spoke core to the boss plate. Japanese Unexamined Utility Model Publication No. 2-133955 describes a steering wheel having a pad and a surface layer, which covers the ring. The pad and surface layer are formed integrally.
In the steering wheel of the above publication, the spoke core and the boss plate include bent portions. The bent portions are engaged and fastened to each other by bolts to connect the steering wheel to the boss plate. Due to this structure, the dimensional accuracy of the portion at which the spoke core is fastened to the boss plate differs between products. This may result in insufficient rigidity of the structure.
Accordingly, it is an objective of the present invention to provide a steering wheel that improves the dimensional accuracy of the fastened portion of the spoke core and the boss plate and also enhances the rigidity of the steering wheel.